<!DOCTYPE html>
<html>
<head>
  <script src="http://code.jquery.com/jquery-latest.js"></script>
</head>
<body>
  <table border="1">

    <tr><td>TD #0</td><td>TD #1</td><td>TD #2</td></tr>
    <tr><td>TD #3</td><td>TD #4</td><td style="text-decoration:line-through;">TD #5</td></tr>

    <tr><td style="text-decoration:line-through;">TD #6</td><td style="text-decoration:line-through;">TD #7</td><td style="text-decoration:line-through;">TD #8</td></tr>
  </table>
<script>$("td:gt(4)").css("text-decoration", "line-through");</script>

</body>
</html>